The present invention relates to a speaker diaphragm using a metal foil such as titanium, aluminium or the like as a substrate thereof, which diaphragm is especially suitable for a tweeter, and a method of making the same.
Hitherto, a product of natural fiber such as pulp, form-forming (blown) high polymer resin, high polymer resin film, metal foil or the like have been used as a materials for speaker diaphragms. However, these are not necessarily satisfactory as diaphragm materials for the following reasons: Diaphragms using a natural fiber product have disadvantages that they are inefficient because of their small specific modulus and are readily influenced by humidity or temperature; although they have an advantage that no adverse sharp resonation occurs during operation because they have appropriate internal mechanical resistance, i.e., attenuation caused by friction among the fibers. Diaphragms using metal foils have the disadvantage that a sharp resonation occurs therein because of their low internal mechanical resistance and a strain appears because of their non-linear motion when amplitude of vibration is great; although they are good in efficiency because they have a relatively high specific modulus and not influenced by humidity or temperature.
It is generally known that for a suitable diaphragm, materials having a high specific modulus, light weight and appropriate internal mechanical resistance are suitable. It has been difficult to provide diaphragms satisfying the abovementioned incompatible characteristics by using existing materials only for the diaphragms.
Although titanium and aluminium, which are generally employed as a metal materials for speaker diaphragms, are mechanically strong and have relatively high specific modulus, that is the ratio of Young's Modulus to the density (e.g. 2.3-2.7.times.10.sup.11 (cm/sec).sup.2), yet, in order to obtain a good efficient speaker, diaphragm materials of a much higher specific modulus are required.